S38 On Gypsum. 



putrefaction of animal substances ; or to decompose 

 manure. Yet we know, from thousands of instances, 

 that it does both ; — freely and amply. It is, too, well 

 established, (see Sir John Pringle^s experiments) that 

 some septics (whether plaster be one or not I do not 

 allege) operate differently on animal and vegetable 

 matter : so as to preserve, or not affect, the one, and 

 putrefy the other. 



He says, its capacity of attracting moisture from 

 the air, in any important quantities ; or its adhesive 

 attraction for it, is *' insignificant and inconsiderable." 

 Yet xve have daily evidence, to shew, most palpa- 

 bly and decisively, and even every farmer's boy, who 

 drives his cattle to and from their pastures, can 

 prove bij his feet, without speculating on causes, 

 that dews and moisture are constantly and profusely 

 retained on plastered fields, for hours, in the early part 

 of the day, after they have passed away from grounds, 

 on which the plaster had not been strewed. If, as he 

 alleges, when combined with ^vater, " it retains that 

 fluid too powerfully to yield it to the roots of the 

 plant," — how can we account for the superior strength 

 and verdure of grass bedewed with the moisture at- 

 tracted, and retained from evaporation, on plastered 

 grounds ; compared with those adjacent, on which no 

 Gypsum has been strewed ? The same difference in 

 the roots, and the whole of the plants, is strikingly per- 

 ceptible : — either in adjacent fields, or strips, purpose- 

 ly left unplastered, in the same field ; in which Mr. 

 D's natural store of gypsum must have been equally 

 deficient, or distributed ? In the evening, too, the dew 

 on plastered ground is the soonest perceived. Until 



